/**
 *3D海洋效应与 Canvas2D
 * 您可以更改注释 "效果属性" 下的属性
 */

// Init Context
let c = document.createElement('canvas').getContext('2d')
let postctx = document.body.appendChild(document.createElement('canvas')).getContext('2d')
let canvas = c.canvas
let vertices = []

// Effect Properties
let vertexCount = 7000
let vertexSize = 3
let oceanWidth = 204
let oceanHeight = -80
let gridSize = 32;
let waveSize = 16;
let perspective = 100;

// Common variables
let depth = (vertexCount / oceanWidth * gridSize)
let frame = 0
let {sin, cos, tan, PI} = Math

// Render loop
let loop = () => {
    let rad = sin(frame / 100) * PI / 20
    let rad2 = sin(frame / 50) * PI / 10
    frame++
    if (postctx.canvas.width !== postctx.canvas.offsetWidth || postctx.canvas.height !== postctx.canvas.offsetHeight) {
        postctx.canvas.width = canvas.width = postctx.canvas.offsetWidth
        postctx.canvas.height = canvas.height = postctx.canvas.offsetHeight
    }


    c.fillStyle = `hsl(200deg, 100%, 2%)`
    c.fillRect(0, 0, canvas.width, canvas.height)
    c.save()
    c.translate(canvas.width / 2, canvas.height / 2)

    c.beginPath()
    vertices.forEach((vertex, i) => {
        let ni = i + oceanWidth
        let x = vertex[0] - frame % (gridSize * 2)
        let z = vertex[2] - frame * 2 % gridSize + (i % 2 === 0 ? gridSize / 2 : 0)
        let wave = (cos(frame / 45 + x / 50) - sin(frame / 20 + z / 50) + sin(frame / 30 + z * x / 10000))
        let y = vertex[1] + wave * waveSize
        let a = Math.max(0, 1 - (Math.sqrt(x ** 2 + z ** 2)) / depth)
        let tx, ty, tz

        y -= oceanHeight

        // Transformation variables
        tx = x
        ty = y
        tz = z

        // Rotation Y
        tx = x * cos(rad) + z * sin(rad)
        tz = -x * sin(rad) + z * cos(rad)

        x = tx
        y = ty
        z = tz

        // Rotation Z
        tx = x * cos(rad) - y * sin(rad)
        ty = x * sin(rad) + y * cos(rad)

        x = tx;
        y = ty;
        z = tz;

        // Rotation X

        ty = y * cos(rad2) - z * sin(rad2)
        tz = y * sin(rad2) + z * cos(rad2)

        x = tx;
        y = ty;
        z = tz;

        x /= z / perspective
        y /= z / perspective


        if (a < 0.01) return
        if (z < 0) return


        c.globalAlpha = a
        c.fillStyle = `hsl(${180 + wave * 20}deg, 100%, 50%)`
        c.fillRect(x - a * vertexSize / 2, y - a * vertexSize / 2, a * vertexSize, a * vertexSize)
        c.globalAlpha = 1
    })
    c.restore()

    // Post-processing
    postctx.drawImage(canvas, 0, 0)

    postctx.globalCompositeOperation = "screen"
    postctx.filter = 'blur(16px)'
    postctx.drawImage(canvas, 0, 0)
    postctx.filter = 'blur(0)'
    postctx.globalCompositeOperation = "source-over"

    requestAnimationFrame(loop)
}

// Generating dots
for (let i = 0; i < vertexCount; i++) {
    let x = i % oceanWidth
    let y = 0
    let z = i / oceanWidth >> 0
    let offset = oceanWidth / 2
    vertices.push([(-offset + x) * gridSize, y * gridSize, z * gridSize])
}

loop()